1. Field of the Invention
The present invention relates to a device for displaying different images to a plurality of viewpoints and to a signal processing method of image data to be displayed. More specifically, the present invention relates to a structure of a display part capable of providing high-quality display images, an image data processing device for transmitting image data for each viewpoint to the display part, and an image data processing method.
2. Description of the Related Art
In accordance with developments in portable telephones and PDAs (personal digital assistants), more and more size reduction and higher definition of the display devices have been achieved. In the meantime, as a display device with a new added values, a display device with which different images are viewed depending on the positions from which viewers observe the display device, i.e., a display device which provides different image to a plurality of viewpoints, and a display device which provides three-dimensional images to the viewer by making the different image as parallax images have attracted attentions.
As a method which provides different images to a plurality of viewpoints, there is known a method which synthesizes and displays image data for each of the viewpoints, separates the displayed synthesized image by an optical separating device formed with a barrier (light-shielding plate) having a lens or a slit, and provides the images to each of the viewpoints. The principle of image separation is to limit the pixels observed from each viewing direction by using an optical device such as a barrier having a slit or a lens. As the image separating device, generally used are a parallax barrier formed with a barrier having a great number of slits in stripes, and a lenticular lens in which cylindrical lenses exhibiting a lens effect in one direction are arranged.
There has been proposed a stereoscopic display device or a multi-viewpoint display device, which includes an optical image separating device such as the one described above and a device which generates synthesized images to be displayed from the image data for each viewpoint (see Japanese Unexamined Patent Publication 2008-109607 (Patent Document 1), for example). Patent Document 1 discloses: a display device which performs stereoscopic display by using a liquid crystal panel and a parallax barrier; and a synthesizing method for creating synthesized images to be displayed on a display part (liquid crystal panel) when performing the stereoscopic display. In this liquid crystal panel, pixel electrodes that form a plurality of sub-pixels are arranged in matrix in the horizontal direction and the vertical direction on the display part. At boundaries between each of the pixel electrodes, scanning lines are provided in the horizontal direction and data lines are provided in the vertical direction. Further, TFTs (thin film transistors) as pixel switching elements are provided in the vicinity of intersection points between the scanning lines and the data lines.
With the stereoscopic display device using the optical image separating device, it is unnecessary for users to wear special eyeglasses. Thus, it is suited to be loaded on portable devices because there is no troublesome work of wearing the eyeglasses. Actually, portable devices to which a stereoscopic display device formed with a liquid crystal panel and a parallax barrier is loaded have been manufactured as products on the market (see NIKKEI ELECTRONICS, Jan. 6, 2003, No. 838 pp. 26-27 (Non-Patent Document 1), for example).
With the above method, i.e., with the display device which provides different images to each of a plurality of viewpoints by using the optical separating device, there may be cases where the boundary between an image and another image is observed dark when the observer changes the viewing position and the image to be observed becomes changed. This phenomenon is caused because a non-display region (a light-shield part generally called a black matrix in liquid crystal panel) between the image and another image for each viewpoint is observed. The above-described phenomenon generated due to the change in the observer's viewing point does not occur in a general display device which does not have an optical separating device. Thus, the observers feel a sense of discomfort or deterioration in the display quality when encountering the above-described phenomenon which is generated in a multi-viewpoint display device or a stereoscopic display device having the optical separating device.
In order to improve the issues generated due to the optical separating device and the light-shield part described above, there is proposed a display device which suppresses deterioration in the display quality through devising the shape and the layout of the pixel electrodes and the light-shield part of the display part (Japanese Unexamined Patent Publication 2005-208567 (Patent Document 2), Japanese Unexamined Patent Publication 2009-098311 (Patent Document 3), for example).
FIG. 134 is a plan view showing a display part of a display device disclosed in Patent Document 2. An aperture part 75 shown in FIG. 134 is an aperture part of a sub-pixel that is the minimum unit of image display. The layout direction of the aperture part 75 in vertical and lateral directions are defined as a vertical direction 11 and a horizontal direction 12, respectively, as shown in FIG. 134. The shape of each aperture part 75 is substantially a trapezoid having features which will be described later. Further, the image separating device is a lenticular lens in which cylindrical lenses 30a having the vertical direction 11 as the longitudinal direction thereof are arranged in the horizontal direction 12. The cylindrical lens 30a does not exhibit the lens effect in the longitudinal direction but exhibits the lens effect only in the lateral direction. That is, the lens effect is achieved for the horizontal direction 12. Thus, light that exits from the aperture parts 75 of a sub-pixel 41 and a sub-pixel 42 neighboring in the horizontal direction 12 is directed towards different directions from each other.
In the aperture part 75, there are a pair of sides which slope towards opposite direction from each other with respect to the vertical direction 11 and the angles thereof between the vertical direction 11 and the extending directions are the same. As a result, along the horizontal direction 12, the position of an edge part of the aperture part 75 of the display panel and the position of the optical axis of the cylindrical lens 30a are relatively different in the vertical direction 11. Further, the aperture parts 75 neighboring to each other along the longitudinal direction are arranged to be line-symmetrical with respect to a segment extending in the lateral direction 12. Furthermore, the aperture parts 75 neighboring to each other along the horizontal direction 12 are arranged to be point-symmetrical with respect to an intersection point between a segment that connects the middle point between the both edges in the vertical direction 11 and a segment that connects the middle point between the both edges in the horizontal direction 12.
Therefore, regarding the aperture widths in the vertical direction 11, the total widths of the aperture part 75 of the sub-pixel 41 and the aperture part 75 of the sub-pixel 42 in the slope parts are substantially constant regardless of the positions in the horizontal direction 12.
That is, in the display device depicted in Patent Document 2, when sectional view of a display panel is assumed in the vertical direction 11 that is perpendicular with respect to the arranging direction of the cylindrical lenses 30a at an arbitrary point along the horizontal direction 12, the proportions of the light-shield parts (wirings 70 and light-shield parts 76) and the aperture parts are substantially the same. Thus, when the observer moves the viewing point to the lateral direction 12 that is the image separating direction so that the observing direction is changed, the proportions of the light-shield parts to be observed are substantially the same. That is, the observer does not observe only the light-shield parts from a specific direction, so that the display is not to be observed dark. That is, it is possible to prevent deterioration in the display quality that is caused due to the light-shield regions.
However, there are following issues with the related techniques described above. With the display device depicted in Patent Document 1, deterioration in the display quality caused due to the light-shield parts is an issue, as described above.
The display device depicted in Patent Document 2 which manages to overcome the issue caused due to the light-shield part needs to keep a complicated relation between the aperture shape of the pixel electrodes of the sub-pixels and the shape of the light-shield parts. Thus, the switching devices (TFTs) to be the light-shield parts cannot be arranged at uniform positions with a pixel electrode unit, such as in the vicinity of the intersection points between the scanning lines and the data lines, unlike the case of Patent Document 1. Further, with the display part of the display device, it is required to have minute pixel pitch for improving the definition and to increase the so-called numerical aperture that is determined with an area ratio of the aperture parts and the light-shield parts which contribute to the display luminance for improving the display luminance. In order to achieve the high numerical aperture while keeping the light-shield part shape and the aperture shape of the display part depicted in Patent Document 2, not only the arranging positions of the switching devices but also the connecting relations between the switching devices and the scanning lines as well as the data lines cannot be determined uniformly with the pixel electrode unit, unlike the case of Patent Document 1. To have nonuniform connecting relations regarding the switching devices of the pixel electrodes, the scanning lines, and the data lines in the pixel electrode unit means that a typical method for generating the synthesized image as depicted in Patent Document 1 cannot be employed.
The present invention has been designed in view of the aforementioned issues. It is an exemplary object of the present invention to provide: a display device capable of displaying images to each of a plurality of viewpoints, which includes a display part in which the shape and layout of the sub-pixels capable of suppressing the issues caused due to the light-shield parts are maintained, and layout and connections of the pixel electrodes, the switching devices, the scanning lines, the data lines, and the like are designed to achieve the high numerical aperture; a display controller of the display device; a device for generating synthesized images to be displayed on the display part; and a method for generating the synthesized images.